57 lines
1.9 KiB
NASM
Executable file
57 lines
1.9 KiB
NASM
Executable file
; bkerndev - Bran's Kernel Development Tutorial
|
|
; By: Brandon F. (friesenb@gmail.com)
|
|
; Desc: Kernel entry point, stack, and Interrupt Service Routines.
|
|
;
|
|
; Notes: No warranty expressed or implied. Use at own risk.
|
|
;
|
|
; This is the kernel's entry point. We could either call main here,
|
|
; or we can use this to setup the stack or other nice stuff, like
|
|
; perhaps setting up the GDT and segments. Please note that interrupts
|
|
; are disabled at this point: More on interrupts later!
|
|
[BITS 32]
|
|
global start
|
|
start:
|
|
mov esp, _sys_stack ; This points the stack to our new stack area
|
|
jmp stublet
|
|
|
|
; This part MUST be 4byte aligned, so we solve that issue using 'ALIGN 4'
|
|
ALIGN 4
|
|
mboot:
|
|
; Multiboot macros to make a few lines later more readable
|
|
MULTIBOOT_PAGE_ALIGN equ 1<<0
|
|
MULTIBOOT_MEMORY_INFO equ 1<<1
|
|
MULTIBOOT_AOUT_KLUDGE equ 1<<16
|
|
MULTIBOOT_HEADER_MAGIC equ 0x1BADB002
|
|
MULTIBOOT_HEADER_FLAGS equ MULTIBOOT_PAGE_ALIGN | MULTIBOOT_MEMORY_INFO | MULTIBOOT_AOUT_KLUDGE
|
|
MULTIBOOT_CHECKSUM equ -(MULTIBOOT_HEADER_MAGIC + MULTIBOOT_HEADER_FLAGS)
|
|
EXTERN code, bss, end
|
|
|
|
; This is the GRUB Multiboot header. A boot signature
|
|
dd MULTIBOOT_HEADER_MAGIC
|
|
dd MULTIBOOT_HEADER_FLAGS
|
|
dd MULTIBOOT_CHECKSUM
|
|
|
|
; AOUT kludge - must be physical addresses. Make a note of these:
|
|
; The linker script fills in the data for these ones!
|
|
dd mboot
|
|
dd code
|
|
dd bss
|
|
dd end
|
|
dd start
|
|
|
|
; This is an endless loop here. Make a note of this: Later on, we
|
|
; will insert an 'extern _main', followed by 'call _main', right
|
|
; before the 'jmp $'.
|
|
stublet:
|
|
extern _main
|
|
call _main
|
|
jmp $
|
|
|
|
; Here is the definition of our BSS section. Right now, we'll use
|
|
; it just to store the stack. Remember that a stack actually grows
|
|
; downwards, so we declare the size of the data before declaring
|
|
; the identifier '_sys_stack'
|
|
SECTION .bss
|
|
resb 8192 ; This reserves 8KBytes of memory here
|
|
_sys_stack:
|
|
|